% echo 10 | perl -e'$_=<>;--$_;print $_=" "x$_."*"." "x$_."\n";print$_ while(s/ \*/\*\*/g&&s/\* /\*\*/g);'
        *
       ***
      *****
     *******
    *********
   ***********
  *************
 ***************
*****************
*******************

package main

import (
   "fmt"
   "strings"
)

func main() {
   fmt.Println("5")
   printStarTree(5)
   fmt.Println("10")
   printStarTree(10)
}

func printStarTree(n int) {
   // Calculate the max number of padded spaces on the left
   spaceCount := (n - 1)/ 2
   var padBuilder strings. Builder
   for j := 0; j < spaceCount; j++ {
       padBuilder.WriteRune(' ')
   }
   padding := padBuilder.String()

   // This string builder is used to accumulate the stars
   var starBuilder strings. Builder
   starBuilder.WriteRune('*')

   // In each iteration, the padding contracts and the stars expand
   for i := 1; i <= n; i += 2 {
       // Print padding + stars
       fmt.Println(padding[:spaceCount] + starBuilder.String())

       // Stars increase at the rate of two per row
       starBuilder.WriteString("**")

       // Reduce padding for the next row
       spaceCount--
   }
}

printStarTree(9)

printStarTree(10)

package main

import (
"fmt"
"strings"
)

func stars(i int) {
// minimize the allocs!
for buf := []byte(strings.Repeat(" ", i*2+1)); i > 0; i-- {
 buf[i] = '*'
 buf[len(buf)-i-1] = '*'
 fmt.Println(string(buf))
}
}

func main() {
stars(3)
stars(5)
stars(10)
}

package main

import (
"fmt"
"strings"
)

func cell(cells []byte, rule int) {
t := [8]byte{}
for i := 0; i < 8; i++ {
 switch rule & 1 {
 case 0:
  t[i] = ' '
 case 1:
  t[i] = 'X'
 }
 rule >>= 1
}
for row := 0; row < 100; row++ {
 fmt.Println(string(cells))
 state := 0
 if cells[0] == 'X' {
  state = 1
 }
 for i := 1; i < len(cells); i++ {
  state = (state << 1) & 7
  if cells[i] == 'X' {
   state = state | 1
  }
  cells[i-1] = t[state]
 }
 state = (state << 1) & 7
 cells[len(cells)-1] = t[state]
}
}

func main() {
buf := []byte(strings.Repeat(" ", 120))

// single X in the middle
buf[len(buf)/2] = 'X'
cell(buf, 18) // 18 = 00010010 binary
}

#include <stdio.h>

int main(void)
{
int rows = 0;
int i = 0;
int j = 0;
int Numspace = 0;
int Numstar = 0;
int Maxstar = 0;

printf("Number of Rows : ");
scanf("%d", &rows);

Maxstar = 2*rows - 1;
for(i = 0; i < rows; i++)
{
 Numstar = 2*i + 1;
 Numspace = (Maxstar - Numstar)/2;
   
 if (Numspace > 0)
  printf("%*c", Numspace, ' ');
 for(j = 0; j < Numstar; j++)
  printf("*");
 printf("\n");

}

return 0;

package main

import (
   "fmt"
   "strings"
)

func main() {
   fmt.Println("Width: 5")
   printStarTreeWidth(5)
   fmt.Println("Width: 10")
   printStarTreeWidth(10)

   fmt.Println("Height: 3")
   printStarTreeHeight(3)
   fmt.Println("Height: 5")
   printStarTreeHeight(5)
}

func printStarTreeHeight(h int) {
   printStarTreeWidth((2 * h) - 1)
}

func printStarTreeWidth(w int) {
   // Calculate the max number of padded spaces on the left
   spaceCount := (w - 1)/ 2
   padding := strings.Repeat(" ", spaceCount)

   // This string builder is used to accumulate the stars
   var starBuilder strings.Builder
   starBuilder.WriteRune('*')

   // In each iteration, the padding contracts and the stars expand
   for i := 1; i <= w; i += 2 {
       // Print padding + stars
       fmt.Println(padding[:spaceCount] + starBuilder.String())

       // Stars increase at the rate of two per row
       starBuilder.WriteString("**")

       // Reduce padding for the next row
       spaceCount--
   }
}